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Researchers at the AFRL Materials and Manufacturing Directorate,
in partnership with Northeastern University, recently developed an
ultra-compact antenna that uses a whole different approach in
transmitting and receiving signals. This breakthrough could be a big
step in the miniaturization of many military and commercial
communication systems.
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September 29, 2017 - Researchers from the AFRL Materials and
Manufacturing Directorate, along with Northeastern University,
developed an ultra-compact antenna smaller than a flea. This
innovation could help miniaturize or add greater functionality to
many devices used by the warfighter. (U.S. Air Force graphic / photo
by Michael McConney)
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Typical antennas rely on size to function effectively in
the electromagnetic spectrum. If the antenna is not long
enough to resonate at the proper frequency, the antenna will
not be able to transmit or receive the desired
electromagnetic waves efficiently. Over the years,
impressive strides have been made in antenna
miniaturization, with cellphones being a prime example.
However, the quality of antennas degrades as they become
smaller, hence the need for cellular carriers to put in
place large numbers of cellular antennas towers to ensure
adequate phone reception for consumers.
“We
identified ultra-compact antennas as the critical last step
in true device miniaturization,” said Dr. Brandon Howe, AFRL
materials scientist. “Researchers had successfully shrunk
most electronic components, but the true miniaturization of
antennas was still a missing piece.”
The size of an
efficient miniature antenna is typically about ten percent
of the wavelength, whereas the ultra-compact AFRL antennas
are as small as fractions of a percent of the wavelength. As
a result, microwave antennas that were previously
approximately a half inch can now be reduced to an object
smaller than a flea (less than one millimeter). Although not
an immediate replacement for small antennas, this
miniaturization could be an important step toward
incorporating antennas into a number of applications for
which they were previously impractical.
These
ultra-compact antennas represent a whole different approach
to this type of technology. Instead of using an
electrically-conductive material to sense the electric field
of microwaves, these antennas use special insulating
materials, called “multiferroic composites.” These materials
are composed of magnetostrictive materials, which convert
magnetism to strain, and piezoelectric materials, which
convert strain to voltage converting material. Using the
multiferroic composites allows the ultra-compact antennas to
function by sensing the magnetic field of microwaves.
“We miniaturized the antennas by borrowing a trick from
acoustic filters in cellphones, which convert microwave
voltages to strain waves. Strain waves travel much slower
than the speed of light, so by doing this, we are able to
shrink the wavelengths while keeping the frequency the same.
This allowed us to make the antennas much smaller,” said
AFRL materials scientist Dr. Michael McConney. He added that
by coating conventional bulk acoustic wave filters with a
magnetic material, these slower strain waves can be
converted into radiation, which enabled them to break the
inefficient scaling laws associated with shrinking typical
antennas to very small sizes.
According to the
researchers, this antenna represents a new way of thinking.
By combining material technologies in a new way, they were
able to reimagine how an antenna functions.
This new
approach allowed the AFRL and Northeastern University
research team to reduce the size of an antenna by over 90
percent, dramatically changing their potential design space.
As McConney explains, this new design allows antennas to
retain much more of their functionality compared to
traditional antennas scaled down to the same size. This
development could result in smaller devices including
wearable antennas, bio-implantable and bio-injectable
antennas, smart phones, and wireless communication systems,
to name a few.
“The miniaturization of military
electronics is of significant benefit to the warfighter, not
only in terms of device size, but in transportability, space
requirements, weight, and many factors,” said Howe. “It can
allow us to fit more into a given space, whether that be in
a field pack or on an aerial platform. It gives us greater
capability in a smaller space.”
The team plans to
continue its research by working toward matching the
ferromagnetic resonance to the acoustic (strain) resonance,
as well as by integrating a new low-loss, highly-sensitive
magnetic material that the group has pioneered. By doing so,
the researchers hope to further enhance the efficiency of
the antenna.
By U.S. Air Force Holly Jordan, AFRL
Provided
through DVIDS
Copyright 2017
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